Carhart-Harris et al. 2016 – Psychological effects of LSD

Fri 06 July 2018

tl;dr:

• Carhart-Harris et al. 2016 gave LSD to 20 healthy-typed people using a placebo design

• Two weeks after the LSD session, they found significant increases in Big-Five Openness and optimism, but no increase in delusional thinking

  • These increases didn't occur after the placebo session

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Carhart-Harris et al. 2016 gave LSD to 20 healthy-typed participants who had previously had a psychedelic experience.

Then they slid the participants into an MRI scanner and imaged their brains. Two weeks later, the participants filled out a bunch of surveys about their psychology.

Actually Carhart-Harris did something cleverer than that – they slid each participant into the MRI machine twice: once after injecting them with LSD, and once after injecting them with a placebo.

As you probably expect, the LSD-injected MRI scans were very different from the placebo-injected MRI scans (examples in this other 2016 Carhart-Harris et al. paper... the man authors a lot of papers).

But that's not very surprising. Of course a person's brain activity looks different while tripping!

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For our purposes, Carhart-Harris 2016 is interesting because of the stuff it found in its psychological surveys:

The LOT-R was chosen as it is a well-validated measure of trait or dispositional optimism (Scheier et al. 1994), the NEO PI-R [NEO Personality Inventory] was chosen as it is well-validated and previous research has shown its sensitivity to the enduring effects of psychedelics (MacLean et al. 2011), and the PDI [Peters’ Delusions Inventory] was chosen as it is a well-validated measure of delusional thinking that has shown to be sensitive to psychotic-like symptoms in the general population (Peters et al. 1999).

Carhart-Harris found:

Optimism was significantly increased 2 weeks after LSD (t=2.91, df=18, p=0.005, Cohen’s d=0.56), as was trait Openness (t=1.95, df=19, p=0.03, Cohen’s d = 0.16) (Fig. 3), and there were no such changes in optimism or personality post-placebo.

Recall that Openness is one of the Big-Five psychological traits, which are tracked by the NEO PI-R.

Implicit here is that the other 4 Big-Five traits did not change after the LSD trip.

Here's a chart of the result:

• Each node is a participant

• Most (but not all) participants became more optimistic and more Open two weeks after the LSD trip

• Some people became way more optimistic after LSD

• The increase in Openness isn't as dramatic

• Both results were significant at p = 0.05

Oh, and they also found that participants weren't more delusional two weeks after LSD than two weeks after placebo, even though the LSD trip itself does resemble psychosis.

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So we can take Carhart-Harris as some evidence that an LSD trip will make most healthy-typed people more optimistic and more Open, two weeks later.

It gets bonus points for being placebo-controlled; most psychedelic studies to date have been open-label (i.e. no placebo).

A few limitations to this study:

• Being inside an MRI tube for 1+ hours during your LSD trip sounds pretty terrible and definitely would effect the trip experience

  • I'm sorta surprised that the Openness and optimism results came through despite the clinical setting of the trips
  • Actually this might be evidence in favor of the robustness of the Openness result

• n = 20, which is very small

• All participants had previously used psychedelics, which probably biases the sample

  • The research team screened for this intentionally for "safety considerations" (i.e. to try to avoid having someone have a bad trip while in a whirring MRI scanner)

• The placebo was only a single-blind (researchers knew who was getting LSD when; participants didn't)

  • Blinding is a difficult problem for psychedelic research because the effects of the drugs break the blind soon after they set in

• Follow-up was short – surveys administered only two weeks after the trip

  • They say a longer-term follow-up is underway, which we're excited to see :-)